Lets say that you have just cut yourself while swimming in the ocean. How much time do you have before the shark gets to you?
It depends three few factors.
The first factor is the shark's sense of smell. Depending on the species, sharks can detect one drop of blood in millions of drops of water, as far as few hundred metres away.
Secondly, it depends on how fast the shark can swim. For example, the great white shark is capable of speed bursts reaching 40 km/h, while the fastest Shortfin mako shark can swim as fast as 50 km/h. They both have a history of lethal attacks on humans.
The last factor is the speed and the direction of the current. If the shark is swimming towards you against the current, it will sense your blood quicker but it will take longer to reach you. If the predator is swimming with the current, it will take longer for the smell to reach its nasal sensory cells but the shark will swim much faster. That means that the lower the speed of downstream current, the more time you have got to escape.
The sharks have been around for at least 420 millions years and they had existed before any vertebrates walked on land. One of the most famous sharks that is Megalodon. According to 2013 study it could reach an astonishing length of up to 20 metres! But you don't have to worry, it is estimated that it became extinct at least 2.6 to million years ago.
Another fascinating and also extinct shark was Helicoprion. It was twice the size of great white shark and had very unusual looking jaw that looked like circular saw blade.
[Helicoprion. Image Source]
Today, I learned!
Other sources used but not included under the hyperlinks:
American Museum of Natural History - "Sharks and Rays: Myth and Reality".
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